Important Notice: Due to a corruption in the BR forum database we regret to announce that data records relating to some of our registered users have been lost. We estimate approx. 500 user details are deleted.

To ease the process of recreating the user IDs we request members that have previously posted on the BR forums to recognise and identify their posts, once the posts are identified please contact the BRF moderator team by emailing BRF Mod Team with your post details.

The mod team will be able to update your username, email etc. so that the user history can be maintained.

Unfortunately for members that have never posted or have had all their posts deleted i.e. users that have 0 posts, we will be unable to recreate your account hence we request that you re-register again.

We apologise for any inconvenience caused and thank you for your understanding.

The Military Issues & History Forum is a venue to discuss issues relating to the military aspects of the Indian Armed Forces, whether the past, present or future. We request members to kindly stay within the mandate of this forum and keep their exchanges of views, on a civilised level, however vehemently any disagreement may be felt. All feedback regarding forum usage may be sent to the moderators using the Feedback Form or by clicking the Report Post Icon in any objectionable post for proper action. Please note that the views expressed by the Members and Moderators on these discussion boards are that of the individuals only and do not reflect the official policy or view of the Bharat-Rakshak.com Website. Copyright Violation is strictly prohibited and may result in revocation of your posting rights - please read the FAQ for full details. Users must also abide by the Forum Guidelines at all times.

1. A 2-stage Main Gear Box was decided during ALH design phase, when the technology collaborator (MBB and ZF Transmission, both from Germany) had little experience for such a design at the higher power ratings of Dhruv.(Apparently it is "revolutionary " large area contact gear design )

2. In 2006 and 2010, CEMILAC chief and IAF Air Marshal have talked abt "design flaws". Delivery started in 2002.

4. Consultancy done with Fiat Avio in 2011 to fix the IDS (Integrated Dynamic System) , of which , ( i think), the Main Gear Box is a part.But whether fix works or speed restrictions remain is still unknown.

5. Manohar Parrikar defended HAL Dhruv in 2015, saying "good machine" after Bolivia crash no. 4 (4 out of 7). But rumor on internet says that a component called a "cyclic" in the MGB-Rotor system was indeed the cause, and is in the Court of Inquiry Report.

6.Dhruv class helos like S-76 and EC-145 have had abt 3 crashes for a production run of 1000. The Dhruv crashed twice in 2017.

7. Another rumor says that Dhruv has no international sales because it is not Internationally certified.

8.From above learnings, it is clear that things are still unclear wrt HAL Dhruv.

Hence the 3-stage Main Gear Box.

But I dunno, all speculation onlee.

In the interests of clarity I would like to raise several questions about this post1.

2. In 2006 and 2010, CEMILAC chief and IAF Air Marshal have talked abt "design flaws". Delivery started in 2002.

This does not necessarily connect with a gearbox problem. In fact airspeed is not the only thing that stresses the gearbox. The engine is put under heavy stress at very high altitudes. On the other hand a lot of aircraft have two different data points. One is "maximum speed achievable" and "maximum speed which should not be exceeded"

3.

Manohar Parrikar defended HAL Dhruv in 2015, saying "good machine" after Bolivia crash no. 4 (4 out of 7). But rumor on internet says that a component called a "cyclic" in the MGB-Rotor system was indeed the cause, and is in the Court of Inquiry Report.

You are holding up and internet rumour against what Parikkar said as an argument. Please provide a source quote and say what a "cyclic" component of a gerabox might be.4

6.Dhruv class helos like S-76 and EC-145 have had abt 3 crashes for a production run of 1000. The Dhruv crashed twice in 2017.

Both 2017 crashes were weather related. What has that got to do with the gearbox?

5.

7. Another rumor says that Dhruv has no international sales because it is not Internationally certified.

Rumour? And how does that connect to the gearbox?

6.

8.From above learnings, it is clear that things are still unclear wrt HAL Dhruv.

There is nothing to learn from your post and nothing to prove about the gearbox. Please educate me on the learnings I have missed.

1. A 2-stage Main Gear Box was decided during ALH design phase, when the technology collaborator (MBB and ZF Transmission, both from Germany) had little experience for such a design at the higher power ratings of Dhruv.(Apparently it is "revolutionary " large area contact gear design )

2. In 2006 and 2010, CEMILAC chief and IAF Air Marshal have talked abt "design flaws". Delivery started in 2002.

4. Consultancy done with Fiat Avio in 2011 to fix the IDS (Integrated Dynamic System) , of which , ( i think), the Main Gear Box is a part.But whether fix works or speed restrictions remain is still unknown.

5. Manohar Parrikar defended HAL Dhruv in 2015, saying "good machine" after Bolivia crash no. 4 (4 out of 7). But rumor on internet says that a component called a "cyclic" in the MGB-Rotor system was indeed the cause, and is in the Court of Inquiry Report.

6.Dhruv class helos like S-76 and EC-145 have had abt 3 crashes for a production run of 1000. The Dhruv crashed twice in 2017.

7. Another rumor says that Dhruv has no international sales because it is not Internationally certified.

8.From above learnings, it is clear that things are still unclear wrt HAL Dhruv.

Hence the 3-stage Main Gear Box.

But I dunno, all speculation onlee.

No such thing called a "cyclic" in the gearbox. Cyclic saturation was the cause of a couple of crashes which is a characteristic of the type of rotor. Its more aerodynamics and flight controls than gear box as such. Please don't believe rumours or spread false statements as facts.

I have written a rebuttal to that matheswaran piece but sadly can't post it here. Matheswaran is not the guy I would trust with things pertaining to indigenous aircraft/helos. This doesn't in any way demean his very significant contribution to the IAF.

You cleverly say that cyclic is not part of MGB but is part of rotor system. then accuse me of "spread false statements as facts".

I request you to clearly bring out these false statements and put them clearly in front of everyone, in the higher interests of "clarity and to prevent spread of bullshit."

A cyclic input is a type of of input to the MRB given by the pilot through the stick via the swashplate. A cyclic input lets you pitch/roll the heli and that is all it does. There is no part called cyclic in a helicopter. Cyclic saturation is a phenomenon again not a part. This can be prevented by various means and it is common on hingeless rotors and since the ALH has such a rotor, cyclic saturation does occur sometimes under certain conditions. A good pilot knows how to avoid getting into such a situation and also knows how to get out of one. Nevertheless a system has been put in place to warn pilots of the situation and thereby prevent cyclic saturation.

raghuk wrote:...A cyclic input is a type of of input to the MRB given by the pilot through the stick via the swashplate. A cyclic input lets you pitch/roll the heli and that is all it does. There is no part called cyclic in a helicopter. Cyclic saturation is a phenomenon again not a part. This can be prevented by various means and it is common on hingeless rotors and since the ALH has such a rotor, cyclic saturation does occur sometimes under certain conditions. A good pilot knows how to avoid getting into such a situation and also knows how to get out of one. Nevertheless a system has been put in place to warn pilots of the situation and thereby prevent cyclic saturation.

Excellent description of the cyclic inputs in rotor system. However, helicopters do have a cyclic. Cyclic is the control stick in the hand of the pilots for cyclic inputs to rotors. It is like the joystick for fixed wing though not exactly same. Helicopter pilots have another control stick called "Collective" for a collective input to all rotor blades.

Also I would not use the term "good pilot" but "experienced pilot" and caution that accidents do happen to these experienced pilots. Mistakes are/can be made by anyone though in-experienced pilots are more prone to errors.

Indranil wrote:Raghuk, Can you answer why HAL went from a 2-stage gear box to a 3-stage gear box on the LUH. Lower wear and tear and maintenance?

I think 'efficiency' i.e. engine size and power being constant (same as ALH engine) only way to vary the SHP at rotor (because rotor size and lift figures for LUH are obviously lesser than ALH) is by introducing more gear ratios and that must have lead them to introduce another stage in the MGB.

I have a video of one of the Ecuador accidents. It was Ecuador and not Bolivia. As far as my theoretical knowledge goes, the helo pilot will change the cyclic to bank, but once the machine has banked to the required angle the cyclic must be set back to a "normal" (or whatever) setting or it will keep banking, and try to roll over. Banking means tilting to one side and has no connection with demonetization for which Modi must answer. In any case a banked helicopter will also show a tendency to sideslip and lose altitude. At low altitudes a sideslip will cause the main rotor to hit the ground. This is what appears to have happened in Ecuador and this I think was what was vaguely blamed on "cyclic"https://www.youtube.com/watch?v=_SSDPtEpw-E

By the way IN's class of ships that runs on latest foreign turbines and transmission from germany cannot reach it's top speed (as per the design goal) ; so things in real life different this tendency to take a microscope and find fault with indigenous products needs to go.

What Raghuk is trying to say is that the cyclic (and the cyclic saturation) has nothing to do with the transmission issues (loosely said, grinding of teeth). The former is to be avoided. The latter, AFAIK, they have contained significantly. The gearbox that go onto ALH is more optimized than the ones that went on Dhruv's built 5 years back. Less weight, less maintenance.

Is there any information in the public domain about Aveo's evaluation of the IDS during 2011 onwards?

Indranil wrote:Raghuk, Can you answer why HAL went from a 2-stage gear box to a 3-stage gear box on the LUH. Lower wear and tear and maintenance?

I think 'efficiency' i.e. engine size and power being constant (same as ALH engine) only way to vary the SHP at rotor (because rotor size and lift figures for LUH are obviously lesser than ALH) is by introducing more gear ratios and that must have lead them to introduce another stage in the MGB.

I could not follow.

The RPMs of the rotors and the engine of both the ALH And LUH must be similar. So it is not about the gear ratios, but the power transferred at those gear ratios. ALH has to transfer twice the amount of power at that gear ratio, and they have already cracked that problem. So why not optimize it down instead of a new 3 stage transmission which will be taller and heavier. Unless the goal is less wear and tear.

shiv wrote:As far as my theoretical knowledge goes, the helo pilot will change the cyclic to bank, but once the machine has banked to the required angle the cyclic must be set back to a "normal" (or whatever) setting or it will keep banking, and try to roll over.

It is not as simple on a heli. In saturation, the pilot does provide input to correct, but that the heli does not respond to those inputs.

If this had been an article in a medical journal I could critique it as a completely worthless one that fails to go into an in depth analysis of how the points that he raises could have been different and how that difference in handling the project might have affected the overall program in terms of import content and cost

The man keeps moving the goalpost. He laments the time delays and cost escalation but then quotes Indian Today and Amnesty International as competent authorities to bash the manufacturer for lack of exports due to imported components. He fails to comment anything about how the project cost and time would have escalated without those imported parts and whether such parts were available at all in India. As an academic article that is a sign of sheer shoddiness. Obviously this cannot be taken as an "academic" work. We have to be Indians and "respect" the air marshal for his seniority

Then he goes on to write about cyclic saturation. He complains that HAL has merely given cockpit warning signs and not solutions, once again saying that MBB did blah blah blah. To me this appears like complete ignorance of the problems faced by engineering design and decisions that have to be taken at various junctures. he blames HAL for lack of experience but there is no indicator of how AM Matheswaran himself is a great expert in engineering design. A brief perusal of what IAF pilots have themselves written shows massive safety problems in aircraft that the IAF bought and ended up loving deeply. Matheswaran quotes India Today somewhere. The same India today has called the MiG 21 a flying coffin. And my late cousin who was a fighter jock in love with MiG 21 wrote about how it would get into a near stall condition without any warning sign at all. Fighter jocks should stay fighter jocks and not act as if they are know-it all experts in design. Gnat pilots have written about the Gnat's unsafe behaviour under various conditions. I don't see Matheswaran types criticizing BAe or Mikoyan in long articles saying "there were no warning signals. Pilots had to cope on their own"

Let me also point out that the man says that MBB should have been retained as consultant but fails to make even one chirp about the HF 24 where the Germans were kept as consultant and yet the plane either failed or was allowed to fail. Blaming a manufacturing or design agency is something I can also do. But looking at the industrial and technical milieu in India and contemplating on solutions and the way forward would amount to what I would call as a scholarly work. This article does not seem like one to me.

That is as unfair a mass of words as any I have seen. Anyone who has some experience of looking at a scientific paper would ask simple questions that remain unanswered in what appears more of a general rant than an informed publication. The man should stick to fighter flying which he was probably good at.

^^^ AM Matheswaran has been much loved on this forum and perhaps has been the one most deconstructed from any service.

On the Cyclic Saturation issue - I have not flown, known or sold a helicopter which does not have bank angle limits and cyclic limits on all axes. There is nothing wrong with ALH which other helicopters do not have or not had. Complex designs always have issues getting identified later and those are solved. The Dhruv went through its own teething challenges and it has overcome those.

Indranil actually on second thoughts ; LUH being smaller and lighter than ALH I would assume would have a smaller rotor so if lift and blade tip speed are limiting factors then LUH rotor will have a higher RPM than the ALH ; at least the general trend seems to support that . So actually I could be wrong about more gear ratios being the reason as amount of sped reduction needed seems to be lesser than that of ALH .

Have been reading about the MGB related posts with interest and have a nube sawal. If the MGB has such limitations that it limits the operations of the Dhruv. Then why have not seen more articles lambasting it and attacking HAL over a poor machine. all indication are that Dhruv is an excellent machine and users are satisfied with it.

Pratyush wrote:Have been reading about the MGB related posts with interest and have a nube sawal. If the MGB has such limitations that it limits the operations of the Dhruv. Then why have not seen more articles lambasting it and attacking HAL over a poor machine. all indication are that Dhruv is an excellent machine and users are satisfied with it.

No?

HAL has as much or as many issues as any other def OEM in the world typically has with any of its products. These machines are quite complex systems. It takes nothing to make snide remarks and deride things, writing columns is easiest thing in the world, but actually making complex systems work is difficult in real life. An ignorant person could give you lecture on some very complex topic of which he knows nothing about with such certainty (we see so many such posts on BRF all the time). Whereas an expert in that field might just say "I can't say" because he understands all the sides of the issue too well. This is applicable to any field not just defense.

Sad to hear the news, regarding the Shakti engine, wasnt there some clause that if order X number, the French were supposed to give TOT to HAL and set up a production base in India. I wonder what happened to that?

are mil helis fitted with ground collision avoidance devices to avoid controlled flight into terrain in foggy or cloudy conditions. in NE the clouds often blanket the hills? over the years we have lost a lot of lives and airframes in NE cloud/fog and sudden weather changes. cloud ceiling is low.

seems like a good fix to implement and COTS solns will be there. civilian planes operate in same terrain. a fokker had crashed into a hill approaching GAU from meghalaya hills once.

Singha imp. point made. I think a v.long time ago,almost 15+ ,the issue was discussed with another helo crash.Essential for use in such terrain/climatic conditions.I think that most helo crashes have been due to bad weather conditions in mountainous terrain.

^ I readily admit to my ignorance on HAL Dhruv, all posts were speculative in nature.

My interest is in the following:

> With the Shakthi engine, we have a 1250 hp capability, with growth potential to 1700 hp. This is the same as a Seaking. SO can we build a Seaking class machine ?

> When searching for answers, I stumbled upon S. Korea , S. Africa and Romania's problems. It seems that , like us, these nations have engine availability. The "helicopter's Achilles heel remains the gearbox." (the collaborator, Airbus Helicopters, is not transferring critical gearbox technology for a Puma class helicopter.)

> Dhruv is a good machine. With Mk IV Version, and Shakthi engines, many shortcomings have been addressed. I was merely attempting to answer Indranil Saar's post about a 3-stage gearbox.I'm still interested in learning from experienced posters on the same.

They have ground collision warnings. But if you are disoriented, those warnings don't help because you don't know which way is where.

But this accident is different. They were para-dropping kerosene jerrycans? From a heli? What altitude where they dropping these from? Does anybody know anything of this procedure and why this is necessitated over just landing the heli and offloading the payload. Or offloading through a winch. With the Mi-17s doors opening at the back this was always going to be tricky.

dinesh_kimar wrote: With the Shakthi engine, we have a 1250 hp capability, with growth potential to 1700 hp. This is the same as a Seaking. SO can we build a Seaking class machine ?

You can. But that would not be able to lift 600 kgs + lots of fuel at 21000 feet. Because, you will be carrying the larger empty weight of a larger heli.

It is not clear to me what is the actual power of the Shakti engine. Numbers like 1067 KW have been consistently floated. But HAL says it is around 895 kW. May be the former is the thermal power generated while the later is the shp. Anyhow, the transmission can handle 825 * 2 kW. So Dhruv does not use the full power of the engines at sea level. But with altitude, the engine performance degrades and it soon becomes the bottleneck. At 21,000 feet Dhruv can lift as much as it can because it has an oversized engine with a very light frame.The same is the story for LUH, and that is why it will trump the Ka-226 at altitude.

Yes, IN did pay the price for ALH. ASR and NSR had conflicting requirements, and ASR won. The same story is being repeated with the IMRH.

The question is: Can a naval variant be developed with a different transmission capable of handling the full power of the engines at sea level and a slightly enlarged cabin? I think this investment in the transmission will be worthwhile, because it means that we will have a Dhruv/LCH version not just for the seas, but also for the plains with longer endurance and payload.

Indranil wrote:But this accident is different. They were para-dropping kerosene jerrycans? From a heli? What altitude where they dropping these from? Does anybody know anything of this procedure and why this is necessitated over just landing the heli and offloading the payload. Or offloading through a winch. With the Mi-17s doors opening at the back this was always going to be tricky.

Terrain would be the mostly likely reason IMHO. A thickly forested hilly area with no LZ. And perhaps they try to do it as low as possible for drop accuracy (to save the ground troops a lot of effort carting the supplies if they fall far from the forward base). Winching would be an option but it might not be the best for this location (load size, risk of snags,...)

Some of the finest warriors these airmen. Total dedication to their job and fellow soldiers. Big loss

Sad at the loss of life. I hope their families will be helped to cope. But I would like to use this opportunity to dig up and diss several cruel misconceptions on BRF that are difficult to rebut when they are stated at other times1. All we talk about is combat combat combat. Lets have multiple racks. More missiles. Bigger this bigger that etc. And the view of the air force is twisted because of that. Transport and logistics are a huge role and go on even at peacetime. This accident should remind us that 24 hours a day 7 days a week some IAF pilots are risking their lives somewhere. Even at peacetime.

2. Flying can be dangerous even without combat, in peacetime. I have actually seen people mock at accidents in peacetime and laugh of BRF and say "Ha ha we won't have any aircraft left for war". I promise to deliver a virtual kick up the backside of the next BRFIte who does that

3. I also promise to deliver a virtual kick up the backside of the next person who says "Soldiers are paid to die". Or better still I won't do that. I will report the post to admins and hope the person gets thrown out. BRF is no place for anyone who says that

Wrt, the mi 17 loss. I have seen program on DD in the old days where the showed IAF helos performing different types of routine air maintainable sorties. One of the techniques ( from the many that were shown) was to throw items from the rear of the helo as it approached the clearing. The helo was in fwd flight while doing so. Why that was done was mostly due to altitude and the need to maintain some margin of safety. In events like that, if the machine hits any kind of turbulence the load will hit the tail boom or the rotor.

May be this is what happened, as at those altitudes the machine has no margin of safety.

Indranil wrote:They have ground collision warnings. But if you are disoriented, those warnings don't help because you don't know which way is where.

But this accident is different. They were para-dropping kerosene jerrycans? From a heli? What altitude where they dropping these from? Does anybody know anything of this procedure and why this is necessitated over just landing the heli and offloading the payload. Or offloading through a winch. With the Mi-17s doors opening at the back this was always going to be tricky.

Yes para dropping from the helicopter is an old and established practice. These para drops are being done on Siachen and NE DZs for a long time. It is part of Air Maintenance task of the IAF to supply forward posts and bases of the IA or associated agencies.

General para drop parameters for Mi 17 are - Height - 100m to 120m on radio altimeter; Speed - 120 kmph, level flight into the wind. The load is held on "skids" (pallets) with 03-04 skid load max at a time. Each skid is tied with parachutes to be dropped on the DZ.

Advantages - At greater elevations/ altitudes the landing load capability of the helicopter drops significantly but the para drop load can still be fairly high / maximum. This reduces the number of sortie per DZ/ post/ base significantly.

- All helipads may not be suitable for landing by larger helicopters and cutting out a suitable helipad may not be feasible.

shiv wrote:3. I also promise to deliver a virtual kick up the backside of the next person who says "Soldiers are paid to die". Or better still I won't do that. I will report the post to admins and hope the person gets thrown out. BRF is no place for anyone who says that

Thanks deejay for the explanation. Did not think of the extra payload angle. What parachutes are used for this. Version of the PTA-M?Also, the typical extraction method through drogue chutes can't be executed because of the tail rotor. How is the payload extracted and the parachute deployed for safe separation.